Modernize WatchServiceFileSystemWatcher and watch .env for dev mode

[gsmet]

Fixes #41282

I can't say I'm a big fan of the fix but we will have to live with this for now.

@stuartwdouglas while working on this, I stumbled upon a small issue: if we are filtering tests, the counter of run tests (All 5 tests are passing (0 skipped)) is not updated when we add filters (even when we force a re-run).
My understanding is that we actually don't clear the test results but only push diffs to the test results (in TestState). I wonder if when we fully rerun the tests, we should actually clear the status but I'm not entirely sure, that's what you wanted?
The reproducer here is quite useful: https://github.com/flyinfish/quarkus--continuous-testing-dotenv . Run dev mode, then uncomment the filters in src/main/resources/application.properties and you should see the problem.

@radcortez at some point, we should probably think of a way to achieve this in a fully supported manner as this thing is quite brittle :). Not sure it's high priority though.

[radcortez]

@radcortez at some point, we should probably think of a way to achieve this in a fully supported manner as this thing is quite brittle :). Not sure it's high priority though.

We could probably use

quarkus/core/runtime/src/main/java/io/quarkus/runtime/configuration/ConfigUtils.java

Lines 75 to 87 in 1d65999

	public static SmallRyeConfigBuilder emptyConfigBuilder() {
	return new SmallRyeConfigBuilder()
	.forClassLoader(Thread.currentThread().getContextClassLoader())
	.withCustomizers(new QuarkusConfigBuilderCustomizer())
	.addDiscoveredConverters()
	.addDefaultInterceptors()
	.addDiscoveredInterceptors()
	.addDiscoveredSecretKeysHandlers()
	.addDefaultSources()
	.withSources(new ApplicationPropertiesConfigSourceLoader.InFileSystem())
	.withSources(new ApplicationPropertiesConfigSourceLoader.InClassPath())
	.withSources(new DotEnvConfigSourceProvider());
	}

and retrieve any required configuration from that instance.

[gsmet]

@radcortez so I went with your idea but went with an even more stripped version of SmallRyeConfig to avoid discovering the converters... could you have a look at the first commit?

@geoand I would appreciate a look at the second commit. I modernized WatchServiceFileSystemWatcher to use java.nio and more modern constructs and also added the ability to monitor a specific file (in this case, the .env).

[geoand]

Seems reasonable, but CI seems to be complaining

[radcortez]

@radcortez so I went with your idea but went with an even more stripped version of SmallRyeConfig to avoid discovering the converters... could you have a look at the first commit?

Perfect!

[gsmet]

Mkay. Doesn't look good. I will have a look at these particular tests...

[quarkus-bot]

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